I want a black background for my tank, and thought about just using black cardboard or paper or felt instead of buying the stick on stuff. But I was wondering how it is to clean the back glass if there is something that is not stuck on the glass. What I mean is, I imagine with the stick on stuff, you can still run a magnetic cleaner across that, right? But with felt or paper, is that harder? Do you have to remove it each time? Or do you just not use magnetic cleaners in the back?